16 Addison E. Verrill, 



to form a square, while in P. argus they are small, situated nearer 

 the median line, and farther apart longitudinally, so that they do 

 not form a square. 



In P. americanus the lateral angular lobes of the abdominal seg- 

 ments have only a single tooth as in P. argus. The basal segment 

 of the antennules is very long, reaching to the middle of the last 

 segment of the peduncle of the antennae. 



The color, as described by Edwards, is very similar to that of 

 P. argus. The abdomen has, like some of the latter, yellow, ocellated 

 spots, a pair on each segment, and also some bands of yellow. But 

 it is not stated that there are four larger spots. 



None of the numerous Bermuda specimens that I have examined 

 agree as well with Edwards' descriptions of P. americanus as with 

 that of P. argus. If the two be distinct, probably the Bermuda 

 records of P. americanus are erroneous. All of our numerous 

 Florida specimens are also P. argus. 



It is not possible to tell whether the P. americanus of Gibbes and 

 of Kingsley were the same, for they gave no descriptions. 



We found a small, parasitic, stalked barnacle attached to the 

 mouth parts, near the efferent opening of the gill cavity of one of 

 the large Bermuda specimens. (See plate XLIII, figs. 5a, 5b.) 

 It appears to be an undescribed species. Dr. H. A. Pilsbry refers 

 it to the genus Octolasrnis, but it has a more calcified shell than 

 most of the species of that genus. 



Octolasmis argus, sp. nov. The body, in a side view, is long 

 ovate, acute distally. It is somewhat swollen proximally ; pedicel 

 is short, strongly wrinkled transversely. The scutum is divided 

 into two very unequal plates. The proximal one is large, some- 

 what oblong, about twice as long as broad, obtuse distally, and with 

 a broad lobe on the carinal edge, defined by two wide shallow 

 emarginations. The distal plate is much smaller, with two emargi- 

 nations on the proximal margin separated by a triangular lobe. 

 Tergum is elongated with its distal end obtuse and corresponding 

 to the notch in the distal tergal plate. The plates are white and 

 well calcified and not widely separated. 



It is related to O. prototypus Pilsbry found on a spider crab at 

 Jamaica (Proc. Acad. N. Sci. Philad., 1911, p. 171). The proxi- 

 mal scutal plate is larger, not triangular, and much longer in pro- 

 portion to its breadth. The tergal plate is not enlarged distally, 

 and the distal scutal plate is smaller and quite different in form. 



